Adler Skywatch: December 2018

Do the days seem to be getting a little darker this month? It’s not your imagination. You can see the change for yourself, along with some of the night’s brightest stars and planets, during the month of December 2018!

This month the Sun rises around 7:00 am CT, and sets before 4:30 pm. That means we get fewer than ten hours of sunlight each day. This trend will continue until around the time of the solstice, which falls on the 21st at 4:23 pm CT. Around that date, the trend reverses; and the daylight hours gradually get longer.

The first week of the month, just after sunset, look very close to the southwest horizon to try to spot the planet Saturn. The evening of the 8th, it’s just above and to the left of an extremely thin waxing crescent Moon—though it may be difficult to see either Saturn or the Moon unless you have a clear view to the southwest. By mid-month Saturn appears so close to the setting Sun that it will be difficult if not impossible to see.

During evening twilight, the planet Mars is about 40 to 45 degrees high in the south-southeast. The night of the 14th it appears a few degrees above a waxing crescent Moon. Mars is low in the west-southwest around 10 p.m. Central time.

Later in the evening, around 11Loo pm, some of the night’s brightest stars form a great circle in the southern skies. Start with the lowest and the brightest star, Sirius, in the constellation Canis Major. Move your line-of-view clockwise and upward to reach the star Procyon, in Canis Minor; followed by Pollux and Castor, the “twin” stars in the constellation Gemini. At the top of the circle is bright Capella, in the constellation Auriga. Continue moving clockwise, but downward, to reach the star Aldebaran, in the constellation Taurus. Further down the circle is Rigel, in the constellation Orion. And further downward and to the left completes the circle back at Sirius.

As morning twilight begins, look for brilliant Venus low in the southeast. The morning of the 3rd, it appears below a waning crescent Moon. After mid-month, as morning twilight brightens the sky, try looking downward from Venus, close to the horizon and about 20 degrees to Venus’s left. With clear skies, you may spot two more planets: bright Mercury and even-brighter Jupiter. The mornings of the 21st and 22nd they appear only about a degree apart, even though the two planets are actually many millions of miles away from each other in space. Mercury drops toward the horizon each morning, but Jupiter climbs higher in the sky through the month.

New Moon: December 7
First Quarter Moon: December 15
Full Moon: December 22
Last Quarter Moon: December 29

**Please note: these descriptions are for the Chicago area, using Central time.